Method and device for delivering radiotherapy

ABSTRACT

A device  10  for aligning a patient for delivering a plurality of radiation beams comprising a patient support surface  12 , a coarse alignment subsystem  14  connected to the patient support surface, and a fine alignment subsystem connected to the patient support surface  16 . A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising compensating for flexion of a radiation beam delivery device within a gantry during movement of the radiation beam delivery device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the radiation beam delivery device so that the target tissue within the patient is placed at the beamline center for the radiation beam delivery device at the second device position.

CROSS-REFERENCE TO RELATED APPLICATION

The present Application is a continuation and claims priority fromInternational Patent Application PCT/US02/34556, titled “Method andDevice for Delivering Radiotherapy,” filed Oct. 28, 2002, which claimsthe benefit of U.S. Provisional Patent Application 60/340,430, filedOct. 30, 2001, entitled “Method and Device for Delivering Radiotherapy,”the contents of which are incorporated herein by reference in theirentirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with United States Government support underCooperative Agreement Number DAMD17-97-2-7016 with the National MedicalTechnology Testbed, Inc., United States Department of the Army. TheUnited States Government has certain rights in this invention.

BACKGROUND

The application of radiation is used for a variety of diagnostic andtherapeutic purposes. For example, external radiotherapy known as“teletherapy” is used to treat approximately half of all patients withcancer in the United States, as well as being used to treat patientswith arterio-venous malformations, intraocular subfoveal neovascularmembranes and Parkinson's disease, among other diseases and conditions.

Generally, teletherapy has been performed using x-ray beams or electronbeams. More recently, however, teletherapy has been performed usingproton beams due to two characteristics of proton beams. First, protonbeams do not scatter as much as either x-ray beams or electron beams.Thus, teletherapy with a proton beam can be applied with a steeper dosegradient near the edge of the proton beam than for an x-ray beam orelectron beam. Second, protons lose energy at a more rapid rate as theypenetrate tissue, thereby delivering a greater dose at the depth of thetarget tissue. These two characteristics of proton beams allow thedelivery of higher doses to target tissues while minimizing radiation toadjacent normal tissues.

The delineation of target tissues from non-target tissues and theselection of beam directions is typically performed using a computerizedtreatment planning system. The computerized treatment planning systemanalyzes input information, such as x-ray axial computed tomography andmagnetic resonance imaging, and provides output information, such asbeam directions, shapes of normal tissue shields for each beam, andpatient alignment information for each beam.

Regardless of the type of teletherapy, however, proper patient alignmentis critical to delivering sufficient radiation to target tissues whileminimizing radiation delivered to non-target tissues. Patient alignmentis the process by which a patient is reproducibly interfaced with theradiation delivery equipment for the purposes of obtaining anatomical,morphological, and physiological information, for performing treatmentsimulations, and for delivering treatments. The goals of patientalignment are to permit unrestricted access to the patient by radiationbeams, and to provide accurate tissue targeting and dose delivery, whilepromoting patient comfort and safety, and allowing for quick patientegress from the radiation delivery equipment.

The five steps in the patient alignment process are registration,immobilization, localization, positioning and verification. Registrationcomprises placing the patient on a patient positioner, such as a movabletable, in a reproducible manner. Immobilization comprises fixing theregistered patient to the patient positioner so that they move togetheras a single unit in a controlled fashion. Localization comprisesdetermining the location of the target tissue relative to thediagnostic, simulation or treatment unit. Positioning comprises movingthe patient positioner to place the target tissue in the desiredorientation at the desired location. Verification comprises verifyingthe patient's orientation and location, and can comprise using the sametechnique as localization. One or more than one of these steps can berepeated as required. If patient alignment is performed rapidly, thepatient is more likely to remain properly aligned, minimizing the marginplaced around the target tissue to account for motion and reducing theradiation dose to non-target tissues.

Patient alignment is usually performed with the patient in a supineposition because a larger surface area of the patient is captured byregistration and immobilization devices, because the entire patient isat a height more accessible to treatment personnel and because patientsare generally more comfortable in the supine position. Most patientpositioners have, therefore, been some form of a table.

Registration is typically accomplished using a registration device suchas a low-density foam that is custom molded to the patient's shape andattached to the top of the patient positioner. The patient lies directlyon the foam, preventing the patient from rolling and translating withrespect to the patient positioner, and increasing patient comfort.

Immobilization is typically accomplished using a thermoplastic net thatattaches to the patient positioner and that covers both the patient andthe registration device. Alternatively, for teletherapy involving thehead and neck, immobilization can be accomplished using a ring referredto as a ‘halo’ that is screwed into the patient's skull and then boltedto the patient positioner.

High precision localization and verification generally rely onradiographic techniques and fiducial markers. The fiducial markers canbe internal, such as natural anatomical landmarks or implantedlandmarks, or can be external such as a z-box attached to a halo.

Localization and verification for proton beam teletherapy typically usesproton beam treatment units that comprise a diagnostic x-ray sourcecapable of projecting an x-ray beam to simulate the intended path of theproton beam. The x-ray beam passes through the patient creatinglocalization images captured on film or by an electronic portal imagingdevice. Localization is achieved by comparing the localization imageswith digitally reconstructed radiographs (DRRS) generated by thetreatment planning system. The patient is repositioned iteratively andnew localization images are generated until coincidence of thelocalization images and digitally reconstructed radiographs are obtainedthereby verifying the location.

After patient alignment has been completed, teletherapy is commonlyperformed using isocentric gantries that facilitate the entry ofradiation beams into patients from multiple directions in a timelymanner. A gantry is a mechanical device that houses a radiation beamdelivery system, and comprises one or more than one instrument, such asa particle accelerator, an x-ray tube, a beam spreading device, beamlimiting collimators, a particle range modifier, a fluence modifyingdevice and a dose monitoring detector.

The rotation axes of the gantry and the patient positioner intersect ata point in space called the isocenter. The center of the target tissuewithin the patient is generally placed at the isocenter. Unfortunately,radiation beam delivery devices within the gantry are prone to flex whenrotated and, thereby, cause misalignment of the radiation beam with thetarget tissue.

Historically, when radiation field alignment was not critical to avoidnormal tissues adjacent to the target tissues, the edges of radiationfields were placed at large distances around the target tissue volumesto ensure that the target tissue would be hit regardless of themisalignment of the radiation beam due to deflections of the radiationbeam delivery system. When critical normal tissues were adjacent totarget tissues, however, precise alignment was achieved either byradiographically repositioning the patient for each individual beam orby using large, rigid, and complex mechanical structures to reducedeflections of radiation beam delivery system. Disadvantageously,however, radiographically repositioning a patient requires at leastabout 15 minutes to align each radiation beam prior to radiationdelivery. Therefore, delivering six beams to a patient requires a totaltreatment time of at least about 1.5 hours. Hence, radiographicallyrepositioning a patient for each radiation beam significantly limits thenumber of patients that can be treated by each treatment apparatus andincreases the cost per treatment.

Therefore, it would be useful to have a method of aligning a patient fordelivering multiple radiation beams, such as proton beams, that allows apatient to be aligned in less time between beam deliveries. Further, Itwould be useful to have a device for aligning a patient for deliveringmultiple radiation beams, such as proton beams, that allows a patient tobe aligned in less time.

SUMMARY

According to one embodiment of the present invention, there is provideda device for aligning a patient for delivering a plurality of radiationbeams. The device comprises a patient support surface, a coarsealignment subsystem connected to the patient support surface, and a finealignment subsystem connected to the patient support surface. In oneembodiment, the patient support surface comprises a table. In anotherembodiment, the coarse alignment subsystem can induce coarse movementsof the patient support surface comprising translation motions of aslarge as about 2 m, and rotations of as large as about 60°. In anotherembodiment, the coarse alignment subsystem comprises an elevatingcolumn. In another embodiment, the coarse alignment subsystem furthercomprises a base and a plurality of wheels connected to the base. Inanother embodiment, the coarse alignment subsystem further comprises abase and a counterweight connected to the base. In another embodiment,the device further comprises electronics to control movement of thecoarse alignment subsystem. In another embodiment, the coarse alignmentsubsystem comprises a position detection system to calculate theposition of the device. In another embodiment, the device furthercomprises an interface for affixing one or more than one registrationand immobilization device connected to the patient support surface. In apreferred embodiment, the fine alignment subsystem can induce finemovements of the patient support surface comprising translation motionsas large as about ±20 mm with a resolution of between about 0.04 mm and0.1 mm resolution in three perpendicular axes, and pitch and rollrotations as large as about ±5° with a resolution of between about 0.1°and 0.2°. In another preferred embodiment, the fine alignment subsystemcan induce fine movements of the patient support surface comprisingtranslation motions as large as about ±20 mm with about 0.05 mmresolution in three perpendicular axes, and pitch and roll rotations ofas large as about ±5° with a resolution of about 0.1°. In anotherembodiment, the device further comprises electronics to control movementof the fine alignment subsystem.

According to another embodiment of the present invention, there isprovided a device for aligning a patient for delivering a plurality ofradiation beams comprising patient support means, coarse alignment meansconnected to the patient support means, and fine alignment meansconnected to the patient support means. In one embodiment, the patientsupport means comprises a table. In another embodiment, the coarsealignment subsystem can induce coarse movements of the patient supportsurface comprising translation motions of as large as about 2 m, androtations of as large as about 60°. In another embodiment, the coarsealignment means comprises an elevating column. In another embodiment,the coarse alignment means further comprises a base and a plurality ofwheels connected to the base. In another embodiment, the coarsealignment means further comprises a base and a counterweight connectedto the base. In another embodiment, the device further compriseselectronics to control movement of the coarse alignment means. Inanother embodiment, the coarse alignment means comprises a positiondetection system to calculate the position of the device. In anotherembodiment, the device further comprises an interface for affixing oneor more than one registration and immobilization means connected to thepatient support means. In a preferred embodiment, the fine alignmentsubsystem can induce fine movements of the patient support surfacecomprising translation motions as large as about ±20 mm with aresolution of between about 0.04 mm and 0.1 mm resolution in threeperpendicular axes, and pitch and roll rotations as large as about ±5°with a resolution of between about 0.1° and 0.2°.

According to another embodiment of the present invention, there isprovided a method of aligning a patient for delivering a plurality ofradiation beams from a plurality of device positions comprisingproviding a device of the present invention. In one embodiment, thedevice has a beamline center, and the method additionally comprisescompensating for flexion of the device during movement of the devicefrom a first device position to a second device position by using a setof predetermined data describing the flexion behavior of the device sothat target tissue within the patient is placed at the beamline centerfor the device at the second device position.

According to another embodiment of the present invention, there isprovided a method of aligning a patient for delivering a plurality ofradiation beams from a plurality of device positions comprisingcompensating for flexion of a radiation beam delivery device having abeamline center during movement of the radiation beam delivery devicefrom a first device position to a second device position by using a setof predetermined data describing the flexion behavior of the radiationbeam delivery device so that the target tissue within the patient isplaced at the beamline center for the radiation beam delivery device atthe second device position.

According to another embodiment of the present invention, there isprovided a method of aligning a patient with a target tissue within thepatient for delivering a plurality of radiation beams from a pluralityof device positions. The method comprises, a) providing a radiation beamdelivery device having a beamline center; b) deriving a set ofpredetermined data describing the flexion behavior of a radiation beamdelivery device; c) selecting a patient having one or more than onetarget tissue suitable for receiving a plurality of radiation beams; d)producing a treatment plan; e) aligning the patient with respect to theradiation beam delivery device oriented at a first device position usingthe derived set of predetermined data describing the flexion behavior ofthe radiation beam delivery device to place the target tissue within thepatient at the beamline center for the first device position; f)delivering a first radiation beam from the first device position to thetarget tissue; g) moving the radiation beam delivery device to a seconddevice position; h) compensating for flexion of the radiation beamdelivery device produced by the move to the second device position usingthe derived set of predetermined data describing the flexion behavior ofthe radiation beam delivery device to place the target tissue within thepatient at the beamline center for the second device position; and i)delivering a second radiation beam from the second device position tothe target tissue within the patient. In one embodiment, the methodfurther comprises a) moving the radiation beam delivery device to athird device position; b) compensating for flexion of the radiation beamdelivery device produced by the move to the third device position usingthe derived set of predetermined data describing the flexion behavior ofa radiation beam delivery device to place the target tissue within thepatient at the beamline center for the third device position; and c)delivering a third radiation beam from the third device position to thetarget tissue within the patient. In another embodiment, selecting apatient having one or more than one target tissue suitable for receivinga plurality of radiation beams comprises selecting a patient having oneor more than one target tissue having a disease or condition amenable toteletherapy. The disease or condition can be selected from the groupconsisting of acoustic neuroma, adenocarcinoma, astrocytoma, chordoma,meningioma, nasopharyngeal carcinoma and pituitary adenoma. In anotherembodiment, aligning the patient with respect to the radiation beamdelivery device oriented at a first device position comprises using atwo-stage patient positioner. In another embodiment, compensating forflexion of the radiation beam delivery device produced by the move tothe second device position comprises using a two-stage patientpositioner and moving the patient and patient positioner as a unit. Inanother embodiment, compensating for flexion of the radiation beamdelivery device produced by the move to the second device positioncomprises one or more than one action selected from the group consistingof shifting an aperture or block holding cone with respect to the beamdelivery apparatus center, shifting the position of beam deliveryapparatus defining collimators, and offsetting the scan pattern of amagnetically scanned beam.

FIGURES

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying figures where:

FIG. 1 is a schematic view of one embodiment of the device for aligninga patient for delivering multiple radiation beams according to thepresent invention;

FIG. 2 is a perspective lateral view of the device in FIG. 1 with thepatient support surface in a neutral position;

FIG. 3 is a side elevational schematic view of the device in FIG. 1showing fine movement of the device in the x-axis;

FIG. 4 is a side elevational schematic view of the device in FIG. 1showing fine movement of the device in the y-axis;

FIG. 5 is a side elevational schematic view of the device in FIG. 1showing fine movement of the device in the z-axis;

FIG. 6 is a side elevational schematic view of the device in FIG. 1showing fine movement of the device in a roll motion;

FIG. 7 is a side elevational schematic view of the device in FIG. 1showing fine movement of the device in a pitch motion;

FIG. 8 is a top cutaway, schematic view of the device in FIG. 1illustrating an example of the components of the device in FIG. 1allowing for fine movement in the x-axis;

FIG. 9 is a top cutaway, schematic view of the device in FIG. 1illustrating an example of the components of the device in FIG. 1allowing for fine movement in the y-axis;

FIG. 10 is a top cutaway, schematic view of the device in FIG. 1illustrating an example of the components of the device in FIG. 1allowing for fine roll movement;

FIG. 11 is a perspective cutaway, schematic view of the device in FIG. 1illustrating an example of the components of the device in FIG. 1allowing for fine pitch movement;

FIG. 12, FIG. 13, FIG. 14 and FIG. 15 are flow charts depicting somesteps of various embodiments of the method of the present invention; and

FIG. 16 and FIG. 17 are examples of plots of data sets describing theflexion behavior of a sample radiation beam delivery device in the planeof gantry rotation, and perpendicular to the plane of gantry rotation,respectively, that can be used with the method of alignment of thepresent invention.

DESCRIPTION

According to one embodiment of the present invention, there is provideda device for aligning a patient for delivering a plurality of radiationbeams, such as proton beams, from a radiation beam delivery device at aplurality of device positions that allows a patient to be aligned inless time than using conventional aligning devices. According to anotherembodiment of the present invention, there is provided a method ofaligning a patient for delivering a plurality of radiation beams, suchas proton beams, from a radiation beam delivery device at a plurality ofdevice positions. The method allows a patient to be aligned in less timethan using conventional methods. By reducing the amount of time foralignment, both the device and the method allow an increased number ofpatients to be treated, decrease the cost of treatment per patient, andreduce the amount of radiation exposure to non-target tissues resultingfrom the alignment process. According to another embodiment of thepresent invention, there is provided a method of performing teletherapy.The method of performing teletherapy comprises aligning a patient usingthe method of aligning of the present invention and delivering aplurality of radiation beams from two or more than two directions.Though disclosed in connection with teletherapy, and especiallyteletherapy utilizing proton beams, the device and method can also beused for aligning a patient for delivering other kinds of radiationaccurately and rapidly to a circumscribed area, for purposes other thanteletherapy, as will be understood by those with skill in the art withreference to this disclosure.

In one embodiment, the present invention is a device for aligning apatient for delivering a plurality of radiation beams that takes lesstime to align the patient between each beam delivery than usingconventional devices. The device can be used with the method of thepresent invention.

The device comprises a two-stage patient positioner. One stage comprisesa coarse alignment subsystem capable of providing large traversals(defined as greater than about 2 m) and large rotations (defined asgreater than about 5°) within the treatment room to place target tissuewithin the patient near the isocenter. The second stage comprises a finealignment subsystem capable of submillimeter translations and subdegreesize rotations to correct for any initial misalignments near isocenter,and to compensate for any deflections in the beam delivery device when aplurality of radiation beams are applied to the target tissue from aplurality of delivery directions.

Referring now to FIG. 1, there is shown a schematic view of oneembodiment of the device of the present invention. As can be seen, thedevice 10 comprises a patient support surface 12, a coarse alignmentsubsystem 14 connected to the patient support system 12 and a finealignment subsystem 16 connected to the patient support surface 12.

The coarse alignment subsystem 14 induces coarse movements of thepatient support surface 12 around the treatment room. In a preferredembodiment, the coarse alignment subsystem 14 can induce coarsemovements of the patient support surface 12 that comprise traversals aslarge as about 4 m and rotations as large as about 200°. In anotherpreferred embodiment, the coarse alignment subsystem 14 can inducecoarse movements of the patient support surface 12 that comprisetraversals as large as about 2 m and rotations as large as about 60°. Ina particularly preferred embodiment, the coarse alignment subsystem 14can induce coarse movements of the patient support surface 12 thatcomprise traversals as large as about 1 m and rotations as large asabout 10°.

As shown in FIG. 1, the coarse alignment subsystem 14 comprises anelevating column 18 connected to the fine alignment subsystem 16, andconnected to a base 20. The coarse alignment subsystem 14 preferablyfurther comprises a plurality of wheels 22 attached to the base 20,which permit the device 10 to translocate around the treatment room. Inone embodiment, the wheels 22 are computer controlled. In anotherembodiment, the coarse alignment subsystem 14 comprises base stand locks24 to maintain a selected position of the device 10 in the treatmentroom. In a preferred embodiment, the coarse alignment subsystem 14comprises a counterweight 26 connected to the base 20 to counterbalancethe weight of the patient support surface 12 and a patient (not shown).Preferably, the coarse alignment subsystem 14 additionally compriseselectronics 29 to control movement of the coarse alignment subsystem 14.In one embodiment, the coarse alignment subsystem 14 further comprises aposition detection system 30 to calculate the position of the device 10in the treatment room. A suitable coarse alignment subsystem 14,including a position detection system 30, can be obtained from ONCOlogMedical QA AB of Uppsala, Sweden under the name Hercules, though thebelt and belt power stage do not need to be installed for incorporationinto the device 10, and the beam axis feature does not need to be usedfor the device 10. Other commercially available coarse alignmentsubsystems and position detection systems are also suitable, as will beunderstood by those with skill in the art with reference to thisdisclosure.

Referring now to FIG. 2, there is shown a perspective side elevationalview of the device 10. As can be seen, the device 10 further comprises apatient support surface 12, such as a table. As shown in FIG. 2, thepatient support surface 12 is in a neutral position, that is, parallelto the long axis of the base 20 and perpendicular to the long axis ofthe elevating column 18. A suitable table is the Atlas patient supportsurface from ONCOlog Medical QA AB, though other patient supportsurfaces are also suitable, as will be understood by those with skill inthe art with reference to this disclosure.

In a preferred embodiment, the device 10 has interfaces 31 for affixingone or more than one registration and immobilization devices, such aswhole body pods, foam cradles, face masks, cranial halos and biteblocks. In another preferred embodiment, as shown, the patient supportsurface 12 comprises an opposing pair of C-shaped arms 28 that link onepart of the patient support surface 12 to another part along itslongitudinal length and that allow the distal end of the patient supportsurface 12 to extend distally, creating an open area that allows aradiation beam to pass into the target tissue unimpeded while thepatient remains supported by one or more than one registration device.Preferably, the C-shaped arms 28 can be rotated away from the beam pathwhile the patient is registered and immobilized on the patient supportsurface 12.

The device 10 further comprises a fine alignment subsystem 16 connectedto the patient support surface 12 and to the coarse alignment subsystem14. The fine alignment subsystem 16 induces fine movements of thepatient support surface 12 with respect to the treatment room. In oneembodiment, the fine movements comprise translation motions of as largeas about ±20 mm with between about 0.04 mm and 0.1 mm resolution inthree perpendicular axes, and pitch and roll rotations of as large asabout ±5° with a resolution of between about 0.1° and 0.2°. In apreferred embodiment, the fine movements comprise translation motions ofas large as about ±20 mm with about 0.05 mm resolution in threeperpendicular axes, and pitch and roll rotations of as large as about±5° with a resolution of about 0.1°.

Referring now to FIG. 3 through FIG. 7, there are shown side elevationalschematic views of the device 10 showing: fine movement of the device 10in the x-axis, FIG. 3; fine movement of the device 10 in the y-axis,FIG. 4; fine movement of the device 10 in the z-axis, FIG. 5; finemovement of the device 10 in a roll motion, FIG. 6; and fine movement ofthe device 10 in a pitch motion, FIG. 6.

Referring now to FIG. 8, there is shown a top cutaway, schematic view ofthe device 10 illustrating an example of the components of the device 10allowing for fine movement in the x-axis. As can be seen, the componentsof the device 10 allowing for fine movement in the x-axis comprise rails32, an x-carrier 34, a driver slot with a ball nut 36, a ball screw 38,a bearing holder 40, a motor with gearbox 42, belt pulleys 44, asynchronizing belt 46, and a 10-turn precision potentiometer 48.

Referring now to FIG. 9, there is shown a top cutaway, schematic view ofthe device 10 illustrating an example of the components of the device 10allowing for fine movement in the y-axis. As can be seen, the componentsof the device 10 allowing for fine movement in the y-axis comprise aframework 50, rails 52, a y-carrier 54, a support driver 56, a driverslot with a ball nut 58, a ball screw 60, a bearing holder 62, a motorwith gearbox 64, belt pulleys 66, a synchronizing belt 68, and a 10-turnprecision potentiometer 70.

Referring now to FIG. 10 there is shown a lateral cutaway, schematicview of the device 10 illustrating an example of the components of thedevice 10 allowing for fine roll movement. As can be seen, thecomponents of the device 10 allowing for fine roll movement comprise alinear actuator 72, a tabletop 74, a center of rotation for roll angle76, a lower center of rotation for the actuator 78, and an upper centerof rotation for the actuator 80. Also shown are the C-shaped arms 28.

Referring now to FIG. 11 there is shown a lateral cutaway, schematicview of the device 10 illustrating an example of the components of thedevice 10 allowing for fine pitch movement. As can be seen, thecomponents of the device 10 allowing for fine pitch movement comprise alinear actuator 82, a tabletop 74, a center of rotation for pitch angle84, a lower center of rotation for the actuator 86, and an upper centerof rotation for the actuator 88.

In another embodiment of the present invention, there is provided amethod of aligning a patient for delivering a plurality of radiationbeams, such as proton beams, from a radiation beam delivery device at aplurality of device positions. Referring now to FIG. 12, FIG. 13, FIG.14 and FIG. 15, there are shown flow charts depicting some steps ofvarious embodiments of the method of the present invention. The methodcomprises compensating for flexion of a radiation beam delivery devicewithin a gantry during movement of the radiation beam delivery devicefrom a first device position to a second device position by using a setof predetermined data describing the flexion behavior of the radiationbeam delivery device so that the target tissue within the patient isplaced at the beamline center for the radiation beam delivery device atthe second device position. The method allows a patient to be irradiatedfrom a plurality of delivery device positions without the patientundergoing a full realignment procedure between repositioning of theradiation beam delivery device from the first device position to thesecond device position. The method advantageously reduces the time andcost for delivering a plurality of radiation beams from a plurality ofdevice positions.

The present method of aligning a patient for delivering a plurality ofradiation beams from a plurality of device positions comprises thefollowing steps. First, a set of data describing the flexion behavior ofa radiation beam delivery device during repositioning is derived. Next,a suitable patient is selected, where the patient has one or more thanone target tissue suitable for receiving a plurality of radiation beams.Then, a treatment plan is produced. Next, the patient is aligned withrespect to a reference set-up position to place the target tissue withinthe patient at the isocenter. Then, the radiation beam delivery deviceis moved to a first device position. Next, flexion of the radiation beamdelivery device produced by the move to the first device position iscompensated for using the set of predetermined data describing theflexion behavior of the radiation beam delivery device to place thetarget tissue within the patient at the beamline center for theradiation beam delivery device at the first device position. Then, afirst radiation beam from the radiation beam delivery device at thefirst device position is delivered to the target tissue within thepatient. Next, the radiation beam delivery device is moved to a seconddevice position. Then, flexion of the radiation beam delivery deviceproduced by the move to the second device position is compensated forusing the set of predetermined data describing the flexion behavior ofthe radiation beam delivery device to place the target tissue within thepatient at the beamline center for the radiation beam delivery device atthe second device position. Next, a second radiation beam from theradiation beam delivery device at the second device position isdelivered to the target tissue within the patient.

In one embodiment, the radiation beam delivery device is moved to athird device position. Then, flexion of the radiation beam deliverydevice produced by the move to the third device position is compensatedfor using the set of predetermined data describing the flexion behaviorof a radiation beam delivery device derived previously. Next, a thirdradiation beam from the radiation beam delivery device at the thirddevice position is delivered to the target tissue within the patient. Aswill be understood by those with skill in the art with reference to thisdisclosure, additional radiation beams from additional device positionscan be delivered to the target tissue within the patient by compensatingfor flexion of the radiation beam delivery device produced by the moveto the additional device positions using the set of predetermined datadescribing the flexion behavior of a radiation beam delivery device.

Each of these steps will now be disclosed in greater detail. First, aset of data describing the flexion behavior of a radiation beam deliverydevice is derived. Referring now to FIG. 16 and FIG. 17, there are shownplots of combined data sets describing the flexion behavior of twosample radiation beam delivery devices at the Loma Linda UniversityProton Treatment Facility, Loma Linda, Calif., US, in the plane ofgantry rotation, FIG. 16, and perpendicular to the plane of gantryrotation, FIG. 17. The measurements were made as follows.

Measurement of the mechanical isocenter was divided into twoperpendicular components. The first component was used to describe theradial deviation as the gantry rotates, while the second componentdescribes the axial runout. The radial component was measured by firstinserting a milled block into the end of the beam delivery deviceclosest to where the patient would be located during a treatment. Themilled block extended from the delivery device to beyond the estimatedvirtual center of the gantry. A theodolite with a 32× magnificationtelescope was placed in the room approximately three meters from thepresumed isocenter and coaxially with it. A grid on the block wasobserved through the theodolite telescope while the gantry was rotatedin increments of 10°. After each movement, the coordinate of the crossin the theodolite sight relative to the grid was recorded. After thedata were measured, they were transformed from the gantry coordinatesystem to the room coordinate system and plotted. The axial runout wasmeasured with a dial indicator that was rigidly affixed to the end ofthe patient positioner with its sensitive point touching the milledblock at the previously determined radial isocenter. Again, the gantrywas rotated in increments of 10°, stopping to record the measurements.Both radial and axial tests were performed in the clockwise andcounterclockwise directions. Circles represent the path of the beamlinecenter during a clockwise rotation while crosses represent the path ofthe beamline center during a counter clockwise rotation.

Next, a suitable patient is selected, where the patient has one or morethan one target tissue suitable for receiving a plurality of radiationbeams. A suitable patient will be one having one or more than one targettissue having a disease or condition amenable to teletherapy, such as asolid tissue neoplasm, an arterio-venous malformations or Parkinson'sdisease. In a preferred embodiment, the patient will have a solid tissueneoplasm susceptible to radiation therapy, such as a neoplasm selectedfrom the group consisting of acoustic neuroma, adenocarcinoma,astrocytoma, chordoma, meningioma, nasopharyngeal carcinoma andpituitary adenoma.

Then, a treatment plan is produced using conventional methods. Forexample, the patient is registered and immobilized to a patientpositioner of a scanner, such as an XCT scanner or other suitabledevice, using appropriate registration and immobilization procedures,and the patient is scanned. The information from the scan is thentransferred to a treatment planning system, and the treatment plan isproduced.

Next, the patient is aligned such that the target tissue within thepatient is at the beamline center of the radiation beam delivery devicefor delivering a first beam of radiation to the target tissue. In oneembodiment, the patient is aligned using a two-stage patient positionerdevice for aligning a patient for delivering a plurality of radiationbeams according to the present invention. This can be accomplished, forexample as follows.

First, the target location within the patient is determined relative toa reference point of the patient positioner. Then, the room coordinatesfor the patient positioner coarse alignment subsystem that are requiredto place the radiation beam delivery device beamline center at thetarget location within the patient are calculated, and these coordinatesare transferred into a patient positioner database to generate aposition file. Next, the patient is taken to the treatment room and thepatient is registered and immobilized to the patient positioner usingthe identical registration and immobilization devices used forgenerating the treatment plan. Then, the fine alignment subsystem iscentered to a neutral position and the coarse alignment subsystem isused to place the target tissue within the patient close to the beamlinecenter for the radiation beam delivery device using the reference pointof the patient positioner. Then, the target tissue location isdetermined using conventional methods, such as using localization x-rayimages, and any discrepancy between the target tissue's present locationand the target tissue's desired location is calculated. Next, thepatient positioner fine alignment subsystem is used to place the targettissue within the patient at the beamline center for the radiation beamdelivery device at the first device position.

After the patient is aligned, a first radiation beam from the firstdevice position is delivered to the target tissue within the patient.Next, the radiation beam delivery device is moved to a second deviceposition. Then, flexion of the radiation beam delivery device producedby the move to the second device position is compensated for using theset of predetermined data describing the flexion behavior of theradiation beam delivery device so that the target tissue within thepatient is placed at the beamline center for the radiation beam deliverydevice at the second device position. In a preferred embodiment,compensation is accomplished by moving the patient and patientpositioner as a unit, such as by using a two-stage patient positionerdevice according to the present invention. In another preferredembodiment, compensation is accomplished by one or more than one actionselected from the group consisting of shifting an aperture or blockholding cone with respect to the center of the beam delivery apparatus,shifting the position of the defining collimators of the beam deliveryapparatus (such as the leaves of a multi-leaf collimator), andoffsetting the scan pattern of a magnetically scanned beam, where eachof these actions can be combined with rotation of the gantry asnecessary to maintain the direction and the aiming point of the beam, aswill be understood by those with skill in the art with reference to thisdisclosure. Next, a second radiation beam from the second deviceposition is delivered to the target tissue within the patient.

The present method can also be used with other therapy deliverytechniques, including serial (fan beam) tomotherapy, spiral (helical)tomotherapy, intensity modulated arc therapy (IMAT), cone beam dynamictherapy (sliding window), or cone beam segmental therapy (step andshoot), as well as being used for diagnostic radiation exposures, aswill be understood by those with skill in the art with reference to thisdisclosure.

Although the present invention has been discussed in considerable detailwith reference to certain preferred embodiments, other embodiments arepossible. Therefore, the scope of the appended claims should not belimited to the description of preferred embodiments contained in thisdisclosure.

What is claimed is:
 1. A device for aligning a patient for delivering a plurality of radiation beams comprising: a) a patient support surface; b) a coarse alignment subsystem connected to the patient support surface; and c) a fine alignment subsystem connected to the patient support surface; where the fine alignment subsystem is configured to move the patient support surface by submillimeter translations and subdegree size rotations to correct for any initial misalignments near isocenter, and to compensate for any deflections in the beam delivery device when a plurality of radiation beams are applied to the target tissue from a plurality of delivery directions.
 2. The device of claim 1, where the patient support surface comprises a table.
 3. The device of claim 1, where the coarse alignment subsystem induces coarse movements of the patient support surface comprising translation motions of as large as about 2 m, and rotations of as large as about 60°.
 4. The device of claim 1, where the coarse alignment subsystem comprises an elevating column.
 5. The device of claim 1, where the coarse alignment subsystem further comprises a base and a plurality of wheels connected to the base.
 6. The device of claim 1, where the coarse alignment subsystem further comprises a base and a counterweight connected to the base.
 7. The device of claim 1, further comprising electronics to control movement of the coarse alignment subsystem.
 8. The device of claim 1, where the coarse alignment subsystem comprises a position detection system to calculate the position of the device.
 9. The device of claim 1, further comprising an interface for affixing one or more than one registration and immobilization device connected to the patient support surface.
 10. The device of claim 1, where the fine alignment subsystem induces fine movements of the patient support surface comprising translation motions as large as about ±20 mm with a resolution of between about 0.04 mm and 0.1 mm resolution in three perpendicular axes, and pitch and roll rotations as large as about ±5° with a resolution of between about 0.1° and 0.2°.
 11. The device of claim 1, where the fine alignment subsystem induces fine movements of the patient support surface comprising translation motions as large as about ±20 mm with about 0.05 mm resolution in three perpendicular axes, and pitch and roll rotations of as large as about ±5° with a resolution of about 0.1°.
 12. The device of claim 1, further comprising electronics to control movement of the fine alignment subsystem.
 13. A device for aligning a patient for delivering a plurality of radiation beams comprising: a) patient support means; b) coarse alignment means connected to the patient support means; and c) fine alignment means connected to the patient support means; where the fine alignment means is configured to move the patient support surface by submillimeter translations and subdegree size rotations to correct for any initial misalignments near isocenter, and to compensate for any deflections in the beam delivery device when a plurality of radiation beams are applied to the target tissue from a plurality of delivery directions.
 14. The device of claim 13, where the patient support means comprises a table.
 15. The device of claim 13, where the coarse alignment subsystem induces coarse movements of the patient support surface comprising translation motions of as large as about 2 m, and rotations of as large as about 60°.
 16. The device of claim 13, where the coarse alignment means comprises an elevating column.
 17. The device of claim 13, where the coarse alignment means further comprises a base and a plurality of wheels connected to the base.
 18. The device of claim 13, where the coarse alignment means further comprises a base and a counterweight connected to the base.
 19. The device of claim 13, further comprising electronics to control movement of the coarse alignment means.
 20. The device of claim 13, where the coarse alignment means comprises a position detection system to calculate the position of the device.
 21. The device of claim 13, further comprising an interface for affixing one or more than one registration and immobilization means connected to the patient support means.
 22. The device of claim 13, where the fine alignment subsystem induces fine movements of the patient support surface comprising translation motions as large as about ±20 mm with a resolution of between about 0.04 mm and 0.1 mm resolution in three perpendicular axes, and pitch and roll rotations as large as about ±5° with a resolution of between about 0.1° and 0.2°.
 23. A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising providing the device of claim
 1. 24. The method of claim 23, where the device has a beamline center, and additionally comprising compensating for flexion of the device during movement of the device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the device so that target tissue within the patient is placed at the beamline center for the device at the second device position.
 25. A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising providing the device of claim
 13. 26. The method of claim 25, where the device has a beamline center, and additionally comprising compensating for flexion of the device during movement of the device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the device so that target tissue within the patient is placed at the beamline center for the device at the second device position.
 27. A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising compensating for flexion of a radiation beam delivery device having a beamline center during movement of the radiation beam delivery device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the radiation beam delivery device so that the target tissue within the patient is placed at the beamline center for the radiation beam delivery device at the second device position.
 28. A method of aligning a patient with a target tissue within the patient for delivering a plurality of radiation beams from a plurality of device positions comprising: a) providing a radiation beam delivery device having a beamline center; b) deriving a set of predetermined data describing the flexion behavior of a radiation beam delivery device; c) selecting a patient having one or more than one target tissue suitable for receiving a plurality of radiation beams; d) producing a treatment plan; e) aligning the patient with respect to the radiation beam delivery device oriented at a first device position using the derived set of predetermined data describing the flexion behavior of the radiation beam delivery device to place the target tissue within the patient at the beamline center for the first device position; f) delivering a first radiation beam from the first device position to the target tissue; g) moving the radiation beam delivery device to a second device position; h) compensating for flexion of the radiation beam delivery device produced by the move to the second device position using the derived set of predetermined data describing the flexion behavior of the radiation beam delivery device to place the target tissue within the patient at the beamline center for the second device position; and i) delivering a second radiation beam from the second device position to the target tissue within the patient.
 29. The method of claim 28, further comprising: a) moving the radiation beam delivery device to a third device position; b) compensating for flexion of the radiation beam delivery device produced by the move to the third device position using the derived set of predetermined data describing the flexion behavior of a radiation beam delivery device to place the target tissue within the patient at the beamline center for the third device position; and c) delivering a third radiation beam from the third device position to the target tissue within the patient.
 30. The method of claim 28, where selecting a patient having one or more than one target tissue suitable for receiving a plurality of radiation beams comprises selecting a patient having one or more than one target tissue having a disease or condition amenable to teletherapy.
 31. The method of claim 30, where the disease or condition is selected from the group consisting or acoustic neuroma, adenocarcinoma, astrocytoma, chordoma, meningioma, nasopharyngeal carcinoma and pituitary adenoma.
 32. The method of claim 28, where aligning the patient with respect to the radiation beam delivery device oriented at a first device position comprises using a two-stage patient positioner.
 33. The method of claim 28, where compensating for flexion of the radiation beam delivery device produced by the move to the second device position comprises using a two-stage patient positioner and moving the patient and patient positioner as a unit.
 34. The method of claim 28, where compensating for flexion of the radiation beam delivery device produced by the move to the second device position comprises one or more than one action selected from the group consisting of shifting an aperture or block holding cone with respect to the beam delivery apparatus center, shifting the position of beam delivery apparatus defining collimators, and offsetting the scan pattern of a magnetically scanned beam.
 35. A device for aligning a patient for delivering a plurality of radiation beams comprising: a) a patient support surface; b) a coarse alignment subsystem connected to the patient support surface; and c) a fine alignment subsystem connected to the patient support surface; where the fine alignment subsystem induces fine movements of the patient support surface comprising translation motions as large as about ±20 mm with a resolution of between about 0.04 mm and 0.1 mm resolution in three perpendicular axes, and pitch and roll rotations as large as about ±5° with a resolution of between about 0.1° and 0.2°.
 36. The device of claim 35, where the patient support surface comprises a table.
 37. The device of claim 35, where the coarse alignment subsystem induces coarse movements of the patient support surface comprising translation motions of as large us about 2 m, and rotations of as large as about 60°.
 38. The device of claim 35, where the coarse alignment subsystem comprises an elevating column.
 39. The device of claim 35, where the coarse alignment subsystem further comprises a base and a plurality of wheels connected to the base.
 40. The device of claim 35, where the coarse alignment subsystem further comprises a base and a counterweight connected to the base.
 41. The device of claim 35, further comprising electronics to control movement of the coarse alignment subsystem.
 42. The device of claim 35, where the coarse alignment subsystem comprises a position detection system to calculate the position of the device.
 43. The device of claim 35, further comprising an interface for affixing one or more than one registration and immobilization device connected to the patient support surface.
 44. The device of claim 35, further comprising electronics to control movement of the fine alignment subsystem.
 45. A device for aligning a patient for delivering a plurality of radiation beams comprising: a) a patient support surface; b) a coarse alignment subsystem connected to the patient support surface; and c) a fine alignment subsystem connected to the patient support surface; where the fine alignment subsystem induces fine movements of the patient support surface comprising translation motions as large as about ±20 mm with about 0.05 mm resolution in three perpendicular axes, and pitch and roll rotations of as large as about ±5° with a resolution of about 0.1°.
 46. The device of claim 45, where the patient support surface comprises a table.
 47. The device of claim 45, where the coarse alignment subsystem induces coarse movements of the patient support surface comprising translation motions of as large as about 2 m, and rotations of as large as about 60°.
 48. The device of claim 45, where the coarse alignment subsystem comprises an elevating column.
 49. The device of claim 45, where the coarse alignment subsystem further comprises a base and a plurality of wheels connected to the base.
 50. The device of claim 45, where the coarse alignment subsystem further comprises a base and a counterweight connected to the base.
 51. The device of claim 45, further comprising electronics to control movement of the coarse alignment subsystem.
 52. The device of claim 45, where the coarse alignment subsystem comprises a position detection system to calculate the position of the device.
 53. The device of claim 45, further comprising an interface for affixing one or more than one registration and immobilization device connected to the patient support surface.
 54. The device of claim 45, further comprising electronics to control movement of the fine alignment subsystem.
 55. A device for aligning a patient for delivering a plurality of radiation beams comprising: a) patient support means; b) coarse alignment means connected to the patient support means; and c) fine alignment means connected to the patient support means; where the fine alignment subsystem induces fine movements of the patient support means comprising translation motions as large as about ±20 mm with a resolution of between about 0.04 mm and 0.1 mm resolution in three perpendicular axes, and pitch and roll rotations as large as about ±5° with a resolution of between about 0.1° and 0.2°.
 56. The device of claim 55, where the patient support means comprises a table.
 57. The device of claim 55, where the coarse alignment subsystem induces coarse movements of the patient support surface comprising translation motions of as large as about 2 m, and rotations of as large as about 60°.
 58. The device of claim 55, where the coarse alignment means comprises an elevating column.
 59. The device of claim 55, where the coarse alignment means further comprises a base and a plurality of wheels connected to the base.
 60. The device of claim 55, where the coarse alignment means further comprises a base and a counterweight connected to the base.
 61. The device of claim 55, further comprising electronics to control movement of the coarse alignment means.
 62. The device of claim 55, where the coarse alignment means comprises a position detection system to calculate the position of the device.
 63. The device of claim 55, further comprising an interface for affixing one or more than one registration and immobilization means connected to the patient support means.
 64. A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising providing the device of claim
 35. 65. The method of claim 64, where the device has a beamline center, and additionally comprising compensating for flexion of the device during movement of the device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the device so that target tissue within the patient is placed at the beamline center for the device at the second device position.
 66. A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising providing the device of claim
 45. 67. The method of claim 66, where the device has a beamline center, and additionally comprising compensating for flexion of the device during movement of the device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the device so that target tissue within the patient is placed at the beamline center for the device at the second device position.
 68. A method of aligning a patient for delivering a plurality of radiation beams from a plurality of device positions comprising providing the device of claim
 55. 69. The method of claim 68, where the device has a beamline center, and additionally comprising compensating for flexion of the device during movement of the device from a first device position to a second device position by using a set of predetermined data describing the flexion behavior of the device so that target tissue within the patient is placed at the beamline center for the device at the second device position. 